Standby Generator - Diesel or NG?

[hwp]

I am thinking about installing a 40kw packaged standby generator but can't decide between diesel and NG. I don't expect it to run a lot - we haven't had a power outage in the 10 years we have lived here. But if we did it would be a disaster. If I thought it would get a lot of use I would definitely go diesel. My guess is that almost all of the run time will be in the weekly automatically scheduled test. The fuel oil tank for the furnace for my garage is very close to where it will be installed so I could use it to run a diesel. But NG is a cheaper and cleaner fuel and should be easier starting. It will take some piping changes to run extend a NG line to the generator but not a big item. It looks like a NG unit is a couple thousand dollars less than a diesel unit. Any suggestions?

 

[MikePA]

I'd go NG. You don't have to worry about filling a tank. How long would a tank of diesel last if you had to run the generator and heat your house?

 

[kennyd]

I would use NG without hesitation if it's available. Why do you need such a large unit?

 

[ToadHill]

NG no doubt, oil stays cleaner, fuel does not spoil as it ages or get contaminated with moisture. Most of the NG units I'm familiar with also have a program that starts them every so often to keep everything from setting up. I'm not sure if diesel units do.

 

[Skyco]

Where do you get the NG? From a local gas utility? Are you positive they'll be in operation during an outage/disaster? Diesel you can haul yourself, NG you can't.
Just food for thought.

 

[hudr]

Have you thought about Propane? Like NG you dont' have the fuel storage issue or the oil getting dirty but you are not tied to the NG infrastructure. We used to have several propane powered tractors and such (still have one old 2 cyl JD) and they just don't wear out. I wish I had been patient enough to wait on a propane powered welder when I bought. Propane would have only added about $200 to the purchase price but it added several weeks to the delivery date. Now they want nearly $800 to do the conversion.
Anyway, a 500 gallon propane tank would run a generator for quite a while. Plus you could get a wet line on it and fill your gas grill tanks or whatever else you had that ran on propane. Also, propane you can also haul yourself if need be.

 

[kenmac]

I don't know what your running but, a 40 kw is a fairly big generator.I would go N.G. myself. A 40 KW is about 680 C.F.H. of N.G.

 

[chh]

If its a short run to your fuel storage tank so you can keep fresh fuel to it diesel wouldn't leave you reliant on the natural gas system. I guess it would be how much confidence you have in it staying in service in a disaster. Any particular reason with going with a 40 kw? That is what I have but it is a leftover from when we had a confinement hog operation. A 40 kw would run that setup and it took a lot of juice. A rule of thumb on generators is to use whatever the number is on your electric transformer. Most houses here are on a 10 kw transformer. But sure and have the transfer switches installed by a qualified electrician. A generator can backfeed down power lines and be fatal to anyone who contacts the "dead" line.
Good luck!

 

[hwp]

Thanks for the various opinions. My inclination is to go with NG.

I have a 400 amp 220 Volt single phase service. By my calculations that 88kVA or 88KW so a 40KW generator would provide less than half maximum possible load, although I doubt I ever get close to that.

My main concern is an electrical outage from ice and wind damage to the overhead wires. As I said before, we haven't had a major power outage in the 10 years we have been here, but we are in a rural area with a lot of trees along the power lines and we do get bad ice storms.

The NG mains are buried so I am not concerned about a gas disruption. If the gas goes out we are in trouble - with or without a power disruption. There is a NG line to a roof top furnace/AC that ends about 60 feet from where the generator would be installed. I would need to increase the size of the line going to the rooftop unit and then extend it to the generator.

Any other comments appreciated.

 

[bearhawk]

Natural Gas...

I think most people put a transfer switch that powers all the essential stuff.

Furnace
Well Pump
Refrigerator
And a few essential outlets / lights

You figure out what the current draw is for the essentials, and size your generator to that. No need to have everything powered up in an emergency.

I think a 10 or 12KW would be plenty.

I have run the above on a 4500 watt portable.

Jim

 

[Tig]

NG for all the reasons listed above. In a major outage you won't find diesel untill the gas station gets a generator fired up. That could be days. We've had two major outages in the past ten years. It's a busy time, especially if you have to feed a generator.

 

[MikePA]

Where do you get the NG? From a local gas utility? Are you positive they'll be in operation during an outage/disaster? Diesel you can haul yourself, NG you can't.

If there's no electricity, how are you going to pump the diesel?

 

[MrJimi]

Just a thought, diesel can and will go bad, natural gas will not
Jim

 

[techman]

I will disagree with the majority. Diesel is much cheaper to operate than NG. At 40 KW you are talking about 200 ft^3/hour. Is your suppl and regulator big enough ?

As far as diesel, it will last years in a storage tank. Keep it closed to minimize moisture, and a stabilizer to prevent algae growth. Most commercial and industrial backup generators are diesel, and fuel is not an issue. Also if it is some sort of major disaster, NG supply could be an issue.

At that size I would not consider NG. Also whatever you get, make sure it is a 1200 RPM driven generator for life and noise.

paul

 

[rosietheriviter]

I will disagree with the majority. Diesel is much cheaper to operate than NG. At 40 KW you are talking about 200 ft^3/hour. Is your suppl and regulator big enough ?

As far as diesel, it will last years in a storage tank. Keep it closed to minimize moisture, and a stabilizer to prevent algae growth. Most commercial and industrial backup generators are diesel, and fuel is not an issue. Also if it is some sort of major disaster, NG supply could be an issue.

At that size I would not consider NG. Also whatever you get, make sure it is a 1200 RPM driven generator for life and noise.
paul

Pros..... NG or LPG are both clean burning, fuel can be stored nearly forever, and contribute to long engine life. Easy starting, low maintenance costs.

Diesel - Long engine life, more HP and KW per cubic inch displacement, much more readily available in low RPM models, in longer term emergencies (disasters or whatever) diesels CAN operate on nearly any oil as fuel (with certain preparation) - that is diesel, heating oil, jet fuel, biodiesel, lube oil, hydraulic oil, vegetable oil, transformer oil, transmission oil, and probably any oil you can think of. Unlimited KW capacity availability.

Cons.... NG or LPG, have certain safety issues (explosive vapors), some concerns with fuel supply (refill) in long term usage, usually of the higher RPM ranges, limited KW capacity availability.

Diesel - stinky, long term fuel storage requirements (to maintain usability of the fuel), heavier machine, usually more expensive to purchase.

I'm sure others will add to this list.

My own preference is diesel (actually diesel welder/generator) I am much more alternative fuel oriented than most. I believe most others will be more interested in the convenience of vaporous fuel though.

By all means, look for the lowest rated operating speed you can buy for the quietest longest lasting unit available!

Rosie

 

[Tig]

I think you would be well advised to do a load calculation to include what you need as opposed to what you have.
With the experience of two major outages keeping me dark for over two weeks, my need list would be;
Water pump.
Furnace fan only.
Limited lighting.
Freezers and fridge.
Computers and network (I work from home)

If I had the choice I would go NG but minimal size to power pump motors, freezers, fans. Turn all the other house breakers off at the panel. Computers and a few lights I would power from a very small battery bank and inverter. I would only start the generator as required. I just don't like the noise and the fuss of having to run a generator 24hrs a day.

 

[ultrarunner]

All good information above.

I power ALL the essential Electrical Loads for a Hospital, including a 20hp ventilation motors with a 125kw Onan Genset with a Turbo Cummins Diesel.

Due to the strict Bay Area Air Quality Regs, I'm only allowed 1 hour per month for testing and exercise... which works out to 30 minutes every other week.

I choose Diesel for ease of refueling in the event of a prolonged outage.

 

[kennyd]

I have a 400 amp 220 Volt single phase service. By my calculations that 88kVA or 88KW so a 40KW generator would provide less than half maximum possible load, although I doubt I ever get close to that.

I have a 400 amp service also, but my B/U gen-set is only 15kw and it runs about 1/2 the house, You do not need to switch the hole house. You can add a new sub-panel and wire the critical circuits to that panel so when the mains go out the gen-set will power the sub-panel.

I have the Generac 15kw that comes with a 16 circuit panel and transfer switch all built in one. It is very similar (older model) to THIS.

 

[RobJ]

All good information above.

I power ALL the essential Electrical Loads for a Hospital, including a 20hp ventilation motors with a 125kw Onan Genset with a Turbo Cummins Diesel.

Due to the strict Bay Area Air Quality Regs, I'm only allowed 1 hour per month for testing and exercise... which works out to 30 minutes every other week.

I choose Diesel for ease of refueling in the event of a prolonged outage.

Bet that sucker sucks the fuel at full load (if it ever gets near a full load, 125kw a bunch!). I'd use NG espacially if it's piped into the house by a utility company. You'll still have gas even it the power is out.

 

[zzvyb6]

Here's 50kw capability. Need more tractor juice to go full tilt. Price was right: $1500.